This invention relates in general to rotating type molding apparatus, and more particularly to a modular unscrewing mold having easily removable and replaceable core assemblies, mountable in a mold base for improving the ease of maintenance and the adaptability of the mold to making articles of different sizes.
Injection molds, especially the types of injection molds used to form threaded articles, such as the plastic closures for bottles and the like, are complex and expensive mechanisms that are manufactured to tight tolerances. When in good repair, such molds can be used to form literally millions of parts per year. However, regular maintenance is required to keep the mold in operating condition. Among the components that require routine servicing are seals, O rings, bearing surfaces, and the like, that wear during normal mold operation.
Unscrewing injection molds of the type referred to above normally include a mold core rotatably mounted in a mold base, and a mold cavity mounted in a cavity retainer plate, movably mounted with respect to the mold base, for movement in a direction perpendicular to the mold base and the cavity retainer plate for bringing the mold core into close proximity to the mold cavity, so that injection molded material may be injected into the space between the core and the cavity to form the molded part.
In known molds, the mold core is rotatably mounted in the mold base by bearings, which are ordinarily press fitted into the base. Conventionally, the core is driven by a reciprocating rack, slidably mounted in the base, which rack engages the core for causing the core to rotate and unscrew from the molded article, as the cavity separates from the core. Typically, the rack is supported by bronze guides mounted in the mold base. Because the mold core is rotatably supported by a multiplicity of bearing components mounted directly in the mold base, the entire mold must normally be disassembled, in order to service or replace the mold core and/or the bearing parts. If a multi-cavity mold, having a multiplicity of mold cores, say 24, experiences damage or wear to one of the cores, the whole mold must be torn down to service the single damaged core.
Because the rotatable mold core of known molds is mounted directly in the mold base, the design of the core and the base are so closely related that the mold core cannot be replaced with a different mold core for forming a different article or a different sized article. Thus, the molds are at least substantially single purpose molds, suitable for forming only closely related parts of substantially similar sizes.
It is an object of this invention to provide modular unscrewing mold apparatus for overcoming the foregoing disadvantages and limitations of known molds. A modular unscrewing mold assembly in accordance with this invention is significantly easier to service or repair than known molds, and is substantially more versatile, having the ability to be adapted to form a wide range of moldable products of different sizes.